Unsupported device...that is in devices.js

I recently posted this on the Home Assistant forum but advised that this forum may be more appropriate…

I’ve recently purchased a CC2531 with the intention of moving zigbee devices from a SmartThings hub so that they are integrated directly with Home Assistant. I think that zigbee2mqtt and mqtt are configured correctly but the first device that I tried to add (Ikea Tradfri LED1623G12 which is in devices.js) appears to have paired but it says that it is not supported
zigbee2mqtt:info 2020-05-30 17:19:32: Currently 1 devices are joined:
zigbee2mqtt:info 2020-05-30 17:19:32: 0x90fd9ffffe112edf (0x90fd9ffffe112edf): Not supported (Router)

When I turn the light off then on I get
zigbee2mqtt:debug 2020-05-30 17:20:42: Device ‘0x90fd9ffffe112edf’ announced itself
zigbee2mqtt:info 2020-05-30 17:20:42: MQTT publish: topic ‘zigbee2mqtt/bridge/log’, payload ‘{“type”:“device_announced”,“message”:“announce”,“meta”:{“friendly_name”:“0x90fd9ffffe112edf”}}’

and then a couple of minutes later
zigbee2mqtt:debug 2020-05-30 17:24:26: Received Zigbee message from ‘0x90fd9ffffe112edf’, type ‘commandQueryNextImageRequest’, cluster ‘genOta’, data ‘{“fieldControl”:1,“manufacturerCode”:4476,“imageType”:8449,“fileVersion”:304170354}’ from endpoint 1 with groupID 0
zigbee2mqtt:warn 2020-05-30 17:24:26: Received message from unsupported device with Zigbee model ‘undefined’
zigbee2mqtt:warn 2020-05-30 17:24:26: Please see: https://www.zigbee2mqtt.io/how_tos/how_to_support_new_devices.html.

I feel like I am swimming in treacle with this and so any help is much appreciated.